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OHM Question - 4x10 cab

Discussion in 'Amps [BG]' started by Bassmaster Doug, Jan 6, 2014.

  1. Bassmaster Doug

    Bassmaster Doug

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    Hi,
    First off, I'm using a SWR 400 watt 4 ohm max amp. I have a GK 4x10 cab which has all the speakers replaced with Fender replacement speakers. When I first got this rig I quickly discovered that 3 of the speakers are 8 ohms and 1 is 16 ohms:meh:. Whith all these wired up the amp would cut out and go into circuit protection mode or something. Thank God it didn't break the amp. So anyway, after discovering this DURING my first band practice, I decided to just disconnect 1 of the 8 ohm speakers and just run the 16 and two 8 ohm'ers. This worked great, but I don't know if it's actually safe to do long term. 2 band practiced later, 1 of my 8 ohm speakers tears the cone and I have a terrible buzzing sound. So I went in and disconnected that one and connected the other 8 ohm I had disconnected from before. I'm back in business(for now at least). So I'm wondering if my jerry-rigged cab is pushing my 8 ohm speakers to hard and that's why one blew. Thanks for any advice.:)
  2. Bass_Pounder

    Bass_Pounder

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    Running mis-matched speakers in the same cab is a recipe for disaster.

    You will probably keep blowing speakers.

    Also, running only 3 of the 4 speakers changes the tuning of the cab, and puts undue stress on the remaining speakers even in the best of situations.

    In your case, someone threw a couple of speakers in without doing the necessary science to make sure the right speakers were used.

    IMO - ditch the cab, and start over.
  3. Bassmaster Doug

    Bassmaster Doug

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    Damn that sucks. I think I'd rather just get 2 more speakers so they all match. But what you're saying does make sense.
  4. B-string

    B-string Supporting Member

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    If you get two more 8 ohm speakers you will need to wire them in series/parallel to protect your amp and not have it fail (8 ohm total load for four 8 ohm speakers wired series/parallel).
  5. BassmanPaul

    BassmanPaul Gold Supporting Member

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    As posted, there is science behind drivers and their enclosures. There in no science whatsoever in your cabinet. You need four identical drivers for the cabinet to work at all. Those drivers will need to be happy with the cabinet design and porting (if any).
  6. Vince Klortho

    Vince Klortho

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    Your amplifier is actually 4Ω minimum - not max. When you hooked that cabinet it up to it, it saw a load of 2.3Ω which is below its minimum. That is why it went into protection mode.

    If you connect four 8Ω speakers together in parallel you will have a 2Ω cabinet and that is too low for your amp. Four 16Ω speakers in parallel will be a 4Ω load and that is perfect for it. Four 8Ω speakers in a parallel+series arrangement will be an 8Ω load and that will work OK with your amp also.
  7. Bassmaster Doug

    Bassmaster Doug

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    Thanks Vince. I think the speakers are in parallel. All the wires are connected to a small board, which is connected to the input jack. It seems if they were in series there would be wires connecting the (-) of one speaker to the (+) of the next. Does that make sense. I'll take a picture of the board and post it on here.
  8. B-string

    B-string Supporting Member

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    Since the amp shut down you can be reasonably sure the cab was wired in parallel. If you still have two good 8 ohm speakers get two that match them exactly and wire your cab like this:
    [​IMG]
  9. Bassmaster Doug

    Bassmaster Doug

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    B-String, I think you're right. Thanks for the info and the pic. That's series/parallel right?
  10. B-string

    B-string Supporting Member

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    Yes, two pairs (top/bottom or sides your choice unless the top and bottom have a divider panel inside) wired in series and those two pairs wired in parallel. If all speakers are 8 ohm the net result is an 8 ohm load.

    Wire two speakers in the same "chamber" together in series if they are divided.
  11. 1n3

    1n3

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    Aside from changing impedance, there's a mechanical consequence when you disconnect a speaker in shared space. The disconnected speaker becomes a passive radiator. That changes loading for the other speakers, increasing the risk of over-excursion... probably how you tore a cone.
  12. Bassmaster Doug

    Bassmaster Doug

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    The cab actually has 4 separate chambers in it. I see now how stupid I was running it how I did.You live and learn I guess.

    These are the two 8ohm's that I have left


    http://www.musiciansfriend.com/accessories/fender-8-ohm-10-replacement-bass-speaker?source=3WWRWXGP&gclid=CKH5t5rB6rsCFWUV7Aod8mAAwg&kwid=productads-plaid^18283950120-sku^660188000000000@ADL4MF-adType^PLA-device^c-adid^30437382507

    So I'll be buying 2 more of these. Hopfully I can find a better price though.
    Does anyone have an opinion on them?
  13. B-string

    B-string Supporting Member

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    All I can offer is they are "special OEM" speakers made by Eminence for Fender. Don't know what basic design was modified for Fender's specs. Eminence may tell you what they are closest to. You "may" find a better price on EvilBay or ask for a better price when ordering.
  14. bgavin

    bgavin Supporting Member

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    I'd bet the GK drivers are a much better match.
  15. B-string

    B-string Supporting Member

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